Talk:Core rope memory

Words/ft&sup3; or bits/ft&sup3;?
> It could store 16 bit words at a density of 36,864 per cubic foot [...]

Hmm, that statement seems a little ambigous to me---see the subject heading. --Wernher 05:00, 9 Jun 2005 (UTC)


 * 36,864 – 16-bit words per cubic foot... -- 205.175.225.5 01:31, 3 November 2005 (UTC)

Density reported low?
I don't think the density figures are correct; the actual density of the AGC memory was higher. I believe what has happened is that the density is computed as the capacity divided by the volume of the entire AGC, rather than just the volume of the core rope memory or core memory sections. --Brouhaha 20:27, 19 May 2006 (UTC)


 * You are right, those density figures are WAY off. According to this long pdf (see pages 87 and 91), The 32,728 bits of core magnetic memory were folded to fit inside a 9 cubic inch module, giving a density of density of about 3630 bits per cubic inch (not including required support circuitry etc). The core rope memory has a density, including all support circuitry, connections and packaging, of 1500 bits per cubic inch.
 * Noccy42 (talk) 07:57, 18 August 2010 (UTC)

Lines per core incorrect
"In the AGC, up to 64 wires could be passed through a single core."

This is incorrect. I'd say whoever wrote it derived this from the fact that each core caries lines for four words (4 x 16 bit word = 64 wires), however this only accounts for the sense lines, and does not include the inhibit lines, or the set and reset line (yes core rope uses inhibit lines just like core memory).

At this time I cannot say exactly how many wires could be passed through a single core (it depends on the internal diameter of the core, and the gauge of the wire), but I can say that a 256 core rope (which is what I believe the ropes in the AGC were, but have no reference for atm), organized in a word per core structure, with 4 words per core, will have 64 sense wires, 8 inhibit wires (2n cores = n inhibit line) and the set and reset wires, which gives the rope a total of 74 wires, with slightly less than that as a potential maximum to pass through any one core (I haven't figured out (or encountered a detailed source for) the actual wiring pattern for the inhibit lines). Noccy42 (talk) 17:37, 17 August 2010 (UTC)


 * According to this, the core rope memory in the AGC was broken into six modules, each containing 512 cores, with 192 sense lines per core, 4 set / reset lines, and 16 inhibit lines.
 * Noccy42 (talk) 08:04, 18 August 2010 (UTC)

Earlier uses?
As I recall, the IBM 360 model 30 used core ROM (for its microcode). If so, that's presumably core rope memory -- which would predate the use in Apollo. Paul Koning (talk) 21:16, 9 April 2008 (UTC)
 * I believe the IBM used Magnetic core memory RAM, but not Core rope memory ROM. I don't know about the model 30, but here's a pic of ROM from a model 20.

-- aBSuRDiST -T ☺ C- 03:52, 8 August 2008 (UTC)
 * The Electrologica X1 is definitely earlier: first delivered in 1958. I updated the text. Paul Koning (talk) 18:18, 24 May 2016 (UTC)

I think the 360/20 and 360/40 used the above tros assemblies for storing microcode. the 30, 50, and 65 used some variation of capacitor storage. On the 360/30 it was in the form of mylar cards exactly the size of a standard tab card with a metallic strip 60 (I think) columns long printed along each of the 12 rows. Holes were punched in the card to indicate a zero bit. Hold the card against the sensing side of the capacitor and impulse the metal strip and out pops the microcode word(s). Minor changes to the microcode could be accomplished by punching a blank ccros card on an ordinary keypunch. — Preceding unsigned comment added by Wplinkage (talk • contribs) 02:37, 3 January 2018 (UTC)

Description of how it actually works?
A example schematic would be handy. This article barely covers anything more technical than "it used a coil" and it is "ROM" instead of RAM.

Anyone got a picture of a full module broke down? That should make it more than clear to anyone with electronics knowledge how it's made. It might even be clear how to design your own. ;) 24.167.39.41 (talk) 11:56, 17 March 2010 (UTC)


 * I agree, this article is seriously lacking details, or even an accurate description. Assuming I can find some decent references, and some appropriate free use images, I will see if I can't fix that. Thus far the best description of how it actually worked I have found is here
 * Noccy42 (talk) 17:37, 17 August 2010 (UTC)


 * As I understand it the Apollo computer used saturable cores, which were inhibited (saturated) to leave only the core on the desired address active, so in this respect they were more like magnetic amplifiers than transformers. Jasen betts (talk) 22:34, 30 January 2016 (UTC)

I agree: This article doesn't even attempt to explain how Rope RAM actually works Gutta Percha (talk) 22:37, 1 March 2014 (UTC)
 * it was read-only - the data was programmed by the pattern of wires, so ROM not RAM Jasen betts (talk) 22:34, 30 January 2016 (UTC)

At about this same time, Honeywell used a similar method on the series 400 for controlling cycle flow and generating the necessary transfer functions, what would now be called microcode. However, instead of calling it rope memory they used a more colorful term, the "Snake" — Preceding unsigned comment added by Wplinkage (talk • contribs) 01:30, 3 January 2018 (UTC)

+1. How does it work?! Meekohi (talk) 15:04, 25 March 2020 (UTC)

No, it isn't transformers
The statement that rope memory uses the cores simply as transformers is incorrect. I'll work on supplying the correct description. That will also make it clear why I mentioned EL X1 ROM; it differs from AGC rope memory in detail but the fundamental principle -- the use of bistable cores and their state transitions -- applies to both. Paul Koning (talk) 20:45, 20 January 2017 (UTC)

Commercial Uses
Wang used what appears to be the same technology for microcode ROM in their programmable calculators, late 1960's and early 1970's. 2048 fine wires woven through 43 "transformers" to form a 2048 43-bit-word ROM. Different form factor (does not resemble rope), but same technology. Wang 700 and 500 Series, and early Wang 600 Series used this technology. They later switched to mask-programmed semiconductor ROMs.

Durgadas311 (talk) 18:21, 23 January 2017 (UTC)


 * Actually, it's not the same technology. The existing article confuses things and implies it is.  Rope memory uses memory type cores (square loop with hysteresis): in the first half of the read cycle, one core is set to 1 while the others remain at 0, then the second half, that core is reset back to 0, producing the data pulses in the sense wires.  The Wang ROM simply uses the cores as transformers (linear, no hysteresis).  Also, the addressing is different: in core rope, the cores do the decoding (essentially implementing a NOR function) while in the Wang ROM, there is a separate wire per address (linear select).  Paul Koning (talk) 18:33, 23 January 2017 (UTC)

Little Old Lady Method
not "Memory" see this https://www.youtube.com/watch?v=P12r8DKHsak&t=60s — Preceding unsigned comment added by 71.114.86.209 (talk) 00:04, 23 January 2023 (UTC)